Air Pressure Regulation in Air Bladders of Ascophyllum nodosum (Fucales, Phaeophyceae)

doi:2006.21.2.245

Algae > Volume 21(2); 2006 > Article

Algae 2006;21(2): 245-251. doi: https://doi.org/10.4490/algae.2006.21.2.245

Angela M. Brackenbury¹^*, Eun Ju Kang² and David J. Garbary¹

¹Department of Biology, St. Francis Xavier University, Antigonish, Nova Scotia, Canada, B2G 2W5
²Department of Oceanography, Chonnam National University, Gwangju 500-757, Korea

ABSTRACT

Diurnal and age-related changes in air pressure were measured in air bladders of Ascophyllum nodosum from the Atlantic coast of Nova Scotia. Exterior and interior bladder volumes vary significantly with 4 and 6 y bladders being about 40% larger than 2 y bladders (p < 0.01). Freshly collected bladders yielded a mean pressure of 40.8 ± 6.5 cm H2O. Overnight (20 h) dark treatment at 15°C generated pressure reductions by 80% in 2 y bladders but only by about 30% in 4 and 6 y bladders. Furthermore, in 2 y bladders 8 out of 11 bladders were reduced to atmospheric pressure. Pressure losses were inversely related to pressure recovery after 2.5 h in natural daylight, but after 5 h in daylight there was no significant difference in pressure within the age groups. Even under 25% of full illumination, bladders inflated to full pressure after 5 h. The results show that differences in bladder age and bladder wall thickness have roles in diurnal patterns of bladder inflation and deflation. These results confirm that bladder inflation is based on photosynthetic O2 production and not on partial pressures of O2 in the surrounding medium as was suggested for Sargassum. Chemical analyses of fluid recovered after the interior of bladders were washed with saline showed no evidence for the occurrence of surfactant that might be responsible for maintaining the air-liquid interface.

Key words: air bladders, air pressure, Ascophyllum, Fucaceae